This invention relates to slip-type expansion joints, such as a multiple ring sealed slip joint, for sealing a steam conduit which passes through a plurality of shells, or casing members, of a steam turbine and, more particularly, to an improved slip-type expansion joint for sealing a steam conduit, wherein the bores of the shells through which the conduit passes are not perfectly registered.
In general, steam turbines operate to convert energy stored in high-pressure, high-temperature steam into rotational mechanical movement. Steam turbines employed by electric utilities in the generation of electric power typically comprise a plurality of turbine blades, or buckets, radially mounted on the periphery of a rotor shaft and disposed so as to form a plurality of bucket wheels. The rotor shaft, with associated bucket wheels, is mounted on bearings with the bucket wheels desposed inside an inner shell which is in turn surrounded by a spaced apart outer shell. This double shell configuration forms a pressurizable housing in which the bucket wheels rotate and prevents potentially damaging thermal gradients. The bucket wheels are disposed between stationary nozzle rings which are formed by circular arrays of stationary curved partitions substantially radially disposed between and fixedly retained by a pair of concentric diaphragm rings. These partitions are generally referred to as nozzle partitions and the spaces between the partitions as nozzles. As steam flows through the interior cavity of the pressurizable inner shell, it alternately passes through stationary nozzle partitions and rotating turbine bucket wheels to produce rotational movement of the shaft. The combination of a pair of diaphragm rings with their associated partitions and the cooperating row of buckets is generally referred to as a stage, stages being numbered sequentially in the direction of steam flow starting from the steam input region.
Modern large steam turbines generally comprise several sections such as, for example, high-pressure, intermediate pressure, low-pressure and reheat. These sections possess various design characteristics so as to permit extraction of an optimum amount of energy from the expansion of steam through the respective turbine sections, thereby optimizing overall turbine efficiency. It is common practice to have one or more of these sections configured in a double flow arrangement, in which steam entering a middle portion, or tub, of the section encounters a diverging flow path. After entry into this middle portion of one of the turbine sections, steam exits in substantially opposite directions, wherein the oppositely directed steam flows are used to impart rotation in the same direction to the turbine shaft. Thus, for example, steam entering from the top or bottom of a turbine section having a horizontally disposed shaft exits toward the left and right to flow generally axially through the turbine. This double flow configuration beneficially contributes to overall machine efficiency. These concepts are elementary and are generally well known in the steam turbine art.
Reference to U.S. Pats. No. 2,112,738 --Doran, issued Mar. 29, 1938; 2,649,315 --Ipsen, issued Aug. 18, 1953; 2,800,299 --Sheppard et al, issued Jul. 23, 1957; 2,815,645 --Downs, issued Dec. 10, 1957 and 2,863,632 --Miller, issued Dec. 9, 1958, and all assigned to the present assignee, indicates that it is known to use conventional slip-type expansion joints at the site of a bore of a member through which a conduit passes for sealing the periphery of the conduit against undesirable passage of steam. These conventional slip-type expansion joints employ a conventional conduit sealing ring having a cylindrical inner surface defining a hole therethrough for sealingly engaging the periphery of the conduit. However, in certain applications, it may be desirable or necessary that the conduit pass through a plurality of spaced apart members, such as shells, each member having a bore therethrough, and the bores registered so that the conduit may pass through the bores and be sealed at each bore by a slip-type expansion joint.
There may be situations, such as when one of the spaced apart members is replaced by a different member after a period of operation, wherein the bores through the members may not exactly align or register to permit the conduit, which is generally rigid, to be installed while still achieving adequate sealing at each bore by a conventional slip-type expansion joint. When it is attempted to insert a conduit through a conventional conduit sealing disposed in a bore ring, wherein the conduit is not aligned with the hole through the sealing ring, the leading edge of the conduit will contact the surface of the hole at different axial extents from the entrance of the hole, which may prohibit further entry of the conduit into the hole. On the other hand, if the conventional sealing ring, which is not generally rigidly secured in the bore during assembly, is placed around the conduit and then reseated in the bore, the lateral sides of the conventional sealing ring will not properly mate with adjacent lateral sealing surfaces in the expansion joint, i.e. the lateral sides of the conventional sealing ring will be skewed with respect to the radial axis of the bore, whenever the conduit is not aligned with the central axis through the bore. Thus, it would be desirable to have a slip-type expansion joint which would sealingly receive a conduit while accommodating a predetermined amount of misalignment between the central axis of the conduit and the central axis of the bore or a predetermined amount of misalignment in the registration of bores through spaced apart turbine members.
Accordingly, it is an object of the present invention to provide an improved slip-type expansion joint at a bore of a turbine member that sealingly receives a conduit, while accommodating misalignment in the registration of bores receiving the same conduit through other spaced apart turbine members.
Another object is to provide an improved slip-type expansion joint at a bore of a turbine member that sealingly receives a conduit, while accommodating misalignment between the central axis of the conduit and the central axis of the bore.
Still another object is to provide an improved slip-type expansion joint which may be readily retrofitted to existing turbine members without hindering operation of the members.
Yet another object is to provide an improved slip type expansion joint at a bore of a member that sealingly receives a conduit, while accommodating misalignment between the designed orientation and the actual orientation of the conduit through the bore.